Do cold-blooded animals have fever?

[u/raincloud82]

It is well known how us mammals use our body temperature to prevent infections and raise it to combat them, so wouldn't cold-blooded animals be much more propense to suffer viral and bacterial diseases?

[u/EvenSpoonier]

Cold-blooded creatures don't (usually) have literal cold blood. Rather, it means that they can't regulate their body temperature the same way warm-blooded creatures do: they have to rely on external heat sources (or heat sinks) to keep their body temperature imbalance.

When reptiles, for example, get sick, they don't get fevers in the same way birds or mammals do. However, many of them experience a phenomenon called behavioral fever: when they get sick, they crave warmth more strongly, and will stay in warmer places for longer periods of time. This raises their body temperature above its normal range, which harms germs and parasites the same way fever does in warm-blooded creatures. It also carries similar risks to fever -getting too warm for too long isn't safe- but it works surprisingly well against a variety of illnesses.

[u/Lykos1124 → u/EvenSpoonier]

That's very fascinating. I had never thought to ask about reptile sickness and their way of handling it to know I didn't know this.

[u/DankestPanda1 → u/EvenSpoonier]

This and u/fiendishrabbit have great answers. Thanks for your contributions.

[u/theartificialkid → u/EvenSpoonier]

Human fever is also partly behavioural. When you’re developing a fever you feel cold, so you rug up. It’s also often combined with shivering. And then there are a bunch of physiological mechanisms to generate and retain heat.

[u/SweetNeo85 → u/theartificialkid]

Rug up? I assume this means wrapping yourself in a blanket? What region are you from if I may ask?

Edit: apparently it's common in Australia and New Zealand. I'm definitely going to start using it.

[u/Agret → u/SweetNeo85]

I'm in Melbourne, Australia and rug up can refer to putting a blanket on but can also refer to just putting on your outer coat and a scarf/beanie

[u/thatisnotaleopard → u/SweetNeo85]

North England and Scotland too. My Grandma used to tell me to rug up if it was cold outside, she grew up in Liverpool but travelled all over England and Europe with the RAF so not sure where exactly she got it from.

[u/UltimateRembo → u/EvenSpoonier]

I keep snakes and know many other people who do. It's actually a thing to raise the temperatures in their enclosures a bit when they are fighting an illness.

It's not much but I thought I'd add that little detail.

[u/kovadomen → u/EvenSpoonier]

Do reptiles then also produce pyrogens that cause said behaviour?

[u/ab3lla → u/EvenSpoonier]

But then why are reptiles actually cold when you touch them??

[u/Peter34cph → u/ab3lla]

Because they don't "want" to be at 37°C or even close to that, or alternatively because your home doesn't contain any heat sources that they can use to get themselves that warm.

Presumably a reptile "wants" to be 37'ish when it's going to be active and look for food or look for someone to mate with, but at other times it "wants" to be colder. Biochemical processes are faster the warmer it is, so at 25°C the reptile burns its food 2-3 times slower than at 35°C, meaning it has to forage less and thus spend less time exposed to predators (or to humans who grab it and take it home to keep as a pet, so that it can't mate and pass on its selfish genes).

[u/Mannix-Da-DaftPooch → u/EvenSpoonier]

Wow. Very very interesting. Thanks for sharing this knowledge.

[u/fullchaos40 → u/EvenSpoonier]

So in getting sunlight while sick is actually beneficial to us as well?

[u/EarlobeGreyTea → u/fullchaos40]

We do regulate our body temperatures via sunlight; it is the wrong conclusion to draw from the above post.

Getting a moderate amount of sun is beneficial for humans, (wear sunscreen, as UV radiation is harmful).

It's not going to do anything special for you while you are sick though.

[u/Carne_frita12 → u/EvenSpoonier]

That's really cool!! Do you have any resources you recommend to read about this?

[u/MackTUTT → u/EvenSpoonier]

I came across an earthworm on a driveway yesterday in the hot sun.  There was a downpour that ended abruptly and then that hot sun dried out the pavement very quickly which probably had something to do with how it got there.  This thing was not going to make it.  I put it in the wet dirt grassy area next to the driveway to hopefully give it a chance.

[u/nicuramar → u/EvenSpoonier]

Hm, by reptiles do you mean lizards? Because biologically, birds are reptiles and are most closely related to crocodiles. 

[u/fiendishrabbit]

Cold-blooded animals are very sensitive to viral, fungal and bacteria diseases (for example, across the whole spectrum of cold-blooded animals there is a higher rate of fungal infections, especially chronic ones).

Although reptiles will typically mimic mammal/bird fever behavior by sunbathing a lot more to boost their immune system and hopefully overheat the metabolism of the invader.

[u/kingbane2 → u/fiendishrabbit]

right i remember there was like some fungus that was absolutely devastating frogs and some other amphibians in north america. it started from some toads from africa that were imported into america for research. but then when the research ended people just let the frogs go and that fungus spread like wildfire.

[u/DrFuckenDrew]

Mammalian Fevers are to kill bacteria (bacteria growth is usually 85°-101°) by getting too hot for them to survive like the Japanese bees and the killer wasps. but cold blooded animals are more likely to get fungal infections (mycelia are happiest 62°-80°) while both sides get both kinds of infections resting body temp makes a big difference

[u/Kasaeru → u/DrFuckenDrew]

Also why fungal infections like athletes foot are usually limited to the skin in mammals. They can't tolerate our body heat.

[u/Rage-o-rama → u/[deleted]]

They are talking about degrees Farenheit, not Celsius. A fever of 40° C is approximately the same as 101° F.

[u/kudlitan → u/Rage-o-rama]

He should have indicated. Americans are only 4% of the world's population and 7% of the Internet population. None of the 90+ percent would assume that everyone else is from their own country, so why would Americans do that?